Priority is claimed to Korean Patent Application No. 2001-82636, filed Dec. 21, 2001, herein incorporated by reference.
1. Field of the Invention
The present invention relates to a method of producing a hardmetal-bonded metal component, and more particularly, to a method of producing a hardmetal-bonded metal component excellent in wear and impact resistance by forming boride spikes in a bonding interface between hardmetal and an iron-based metal body to increase the bond strength therebetween.
2. Description of the Prior Art
Hardmetal comprises hard particles such as carbides including tungsten carbide and chromium carbide, nitrides or borides, and a metallic binder such as single metal including nickel and cobalt or alloy including nickel-based or cobalt-based alloy. By virtue of its excellent wear resistance, the hardmetal has been widely used in the field of tools and mechanical parts requiring high wear resistance.
In order for the hardmetal to be used as mechanical parts, it is generally bonded to a metal body such as iron-based alloy through the use of a brazing metal. In the meantime, the brazing metal should be excellent in bondability to both the hardmetal and the metal body to assure that the superhard alloy is bonded to the body with an increased strength. More particularly, the mechanical characteristics of the bonded component tend to be deteriorated due to the poor mechanical properties of the brazing metal itself.
To avoid such deficiency, a number of methods have been proposed of bonding hardmetal directly to a body without having to use any brazing metal. Japanese Patent Laid-Open Publication Nos. 62-182407 and 62-185806 disclose some of the direct bonding methods. However, mechanical components produced by way of such direct bonding techniques have a generally smooth bonding interface, which makes it difficult to increase the bond strength to above a certain limit. Furthermore, the direct bonding techniques cannot be employed in producing those wear-resistant parts which are frequently exposed to high surface pressure environment when in use.
Under the circumstances, there has been also proposed a method of forming, by machining, complementary protrusions and recesses on the bonding surfaces of the hardmetal sintered body and the metal body and then causing the sintered body and the metal body to be bonded together. This method poses a drawback that air voids are created in the bonding interface, thus resulting in a reduced bond strength.
Accordingly, the present invention is contemplated to solve the above and other shortcomings inherent in the prior art solutions and it is an object of the present invention to provide a method capable of bonding a superhard alloy preform to an iron-based metal body with a high bond strength and without having to use any brazing metal, thereby producing a hardmetal-bonded metal component which has an excellent wear and impact resistance.
According to an aspect of the present invention, there is provided a method of producing a hardmetal-bonded metal component, comprising the steps of: providing an iron-based metal body; mixing and compressing raw material powder of superhard alloy and binder powder containing nickel, silicon and boron into a preform; heating and sintering the preform; and applying heat to the sintered body and the iron-based metal body under a state that the sintered body is brought into contact with the iron-based metal body, to thereby cause the sintered body to be bonded to the iron-based metal body, wherein the sintered body and the iron-based metal body are thermally treated at a temperature of 1000 to 1200xc2x0 C. for 30 or more minutes so that boron present in the sintered body is infiltrated into grain boundaries of the iron-based metal body, and have reaction with elements of metal body to form a plurality of boride spikes in a bonding interface.
The silicon and boron are preferably added in the amount of 2 to 6 wt % and 2 to 5 wt-%, respectively, on the basis of binder powder weight. Further, the raw material powder of hardmetal is preferably selected from the group consisting of carbides, nitrides and borides. Further, the duration time of the heat treatment preferably ranges from 60 to 100 minutes.